U.S. patent application number 11/203045 was filed with the patent office on 2007-02-15 for methods and compositions for reducing the viscosity of treatment fluids used in subterranean operations.
This patent application is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to Phillip C. Harris, Stanley J. Heath.
Application Number | 20070034376 11/203045 |
Document ID | / |
Family ID | 37054726 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070034376 |
Kind Code |
A1 |
Harris; Phillip C. ; et
al. |
February 15, 2007 |
Methods and compositions for reducing the viscosity of treatment
fluids used in subterranean operations
Abstract
Methods and compositions for reducing the viscosity of
subterranean treatment fluids that comprise a gelling agent
utilizing breakers that comprise hydroquinone and/or a derivative
thereof. In one embodiment, the present invention provides a method
comprising: providing a treatment fluid that comprises an aqueous
base fluid and a gelling agent; providing a breaker that comprises
a hydroquinone component; allowing the breaker to interact with the
treatment fluid; and allowing the breaker to at least partially
reduce the viscosity of the treatment fluid.
Inventors: |
Harris; Phillip C.; (Duncan,
OK) ; Heath; Stanley J.; (Duncan, OK) |
Correspondence
Address: |
Robert A. Kent
2600 S. 2nd Street
Duncan
OK
73536-0440
US
|
Assignee: |
Halliburton Energy Services,
Inc.
|
Family ID: |
37054726 |
Appl. No.: |
11/203045 |
Filed: |
August 12, 2005 |
Current U.S.
Class: |
166/300 ;
166/308.3; 166/308.5; 507/263; 507/921 |
Current CPC
Class: |
C09K 8/706 20130101;
C09K 8/68 20130101; C09K 8/685 20130101; C09K 8/70 20130101 |
Class at
Publication: |
166/300 ;
166/308.3; 166/308.5; 507/263; 507/921 |
International
Class: |
E21B 43/26 20060101
E21B043/26; E21B 43/22 20060101 E21B043/22 |
Claims
1. A method comprising: providing a treatment fluid that comprises
an aqueous base fluid and a gelling agent the treatment fluid
having a pH in the range of from about 3 to about 12; providing a
breaker that comprises a hydroquinone component; allowing the
breaker to interact with the treatment fluid; and allowing the
viscosity of the treatment fluid to reduce.
2. The method of claim 1 wherein the aqueous base fluid is selected
from the group consisting of fresh water, saltwater, brines,
seawater, and combinations thereof.
3. The method of claim 1 wherein the gelling agent is selected from
the group consisting of hydroxyethyl guar, hydroxypropyl guar,
carboxymethyl guar, carboxymethylhydroxyethyl guar,
carboxymethylhydroxypropyl guar, hydroxyethyl cellulose,
carboxyethylcellulose, carboxymethylcellulose,
carboxymethylhydroxyethylcellulose, derivatives thereof, and
combinations thereof.
4. The method of claim 1 wherein the hydroquinone component is
selected from the group consisting of hydroquinone, semiquinone,
benzoquinone, catechol, quinhydrone charge-transfer complexes,
derivatives thereof, and combinations thereof.
5. The method of claim 1 wherein the breaker is present such that
the hydroquinone component is present in an amount in the range of
from about 0.001% to about 0.3% by weight of the treatment
fluid.
6. The method of claim 1 wherein the gelling agent comprises a
crosslinked gelling agent wherein at least a portion of the gelling
agent is crosslinked by a crosslinking reaction comprising a
crosslinking agent.
7. The method of claim 6 wherein the crosslinking agent is selected
from the group consisting of boric acid, disodium octaborate
tetrahydrate, sodium diborate, pentaborates, ulexite, colemanite,
zirconium lactate, zirconium lactate triethanolamine, zirconium
carbonate, zirconium acetylacetonate, zirconium malate, zirconium
citrate, zirconium diisopropylamine lactate, zirconium glycolate,
titanium lactate, zirconium triethanol amine glycolate, zirconium
lactate glycolate, zirconium triethanol amine, titanium malate,
titanium citrate, titanium ammonium lactate, titanium
triethanolamine, titanium acetylacetonate, aluminum lactate,
aluminum citrate, antimony compounds, chromium compounds, iron
compounds, copper compounds, zinc compounds, derivatives thereof,
and combinations thereof.
8. The method of claim 1 wherein the breaker further comprises at
least one component selected from the group consisting of sodium
chlorite, sodium bromate, sodium persulfate, sodium
peroxydisulfate, ammonium chlorite, ammonium bromate, ammonium
persulfate, ammonium peroxydisulfate, potassium chlorite, potassium
bromate, potassium persulfate, potassium peroxydisulfate,
oxidizable metal ions, derivatives thereof, and combinations
thereof.
9. (canceled)
10. The method of claim 1 wherein the pH of the treatment fluid is
in the range of from about 4 to about 6.
11. The method of claim 1 wherein the breaker that comprises the
hydroquinone component is provided in the same step as providing
the treatment fluid.
12. The method of claim 1 further comprising introducing the
treatment fluid into at least a portion of a subterranean
formation.
13. The method of claim 12 further comprising recovering the
treatment fluid from the subterranean formation.
14. A method of treating a portion of a subterranean formation
comprising: providing a treatment fluid that comprises an aqueous
base fluid and a gelling agent, the treatment fluid having a pH in
the range of from about 3 to about 12; providing a breaker that
comprises a hydroquinone component; introducing the treatment fluid
into the portion of the subterranean formation; introducing the
breaker into the portion of the subterranean formation such that
the breaker interacts with the treatment fluid; and allowing the
viscosity of the treatment fluid to reduce.
15. The method of claim 14 wherein the treatment fluid further
comprises a plurality of particulates.
16. The method of claim 14 wherein the gelling agent comprises a
crosslinked gelling agent wherein at least a portion of the gelling
agent is crosslinked by a crosslinking reaction comprising a
crosslinking agent.
17. The method of claim 14 wherein introducing the treatment fluid
into the portion of the subterranean formation comprises
introducing the treatment fluid at or above a pressure sufficient
to create or enhance one or more fractures in the subterranean
formation.
18. The method of claim 14 further comprising recovering the
treatment fluid from the subterranean formation.
19. (canceled)
20. The method of claim 21 wherein the gelling agent comprises a
crosslinked gelling agent wherein at least a portion of the gelling
agent is crosslinked by a crosslinking reaction comprising a
crosslinking agent.
21. A method comprising: providing a treatment fluid that comprises
an aqueous base fluid and a gelling agent; providing a breaker that
comprises a hydroquinone component, the breaker being substantially
free of ammonium persulfates and alkali metal persulfates; allowing
the breaker to interact with the treatment fluid; and allowing the
viscosity of the treatment fluid to reduce.
22. The method of claim 14 wherein the breaker that comprises the
hydroquinone component is provided in the same step as providing
the treatment fluid.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to co-pending U.S. patent
application Ser. No. ______, Attorney Docket Number HES
2005-IP-017048U2, entitled "Methods and Compositions for Reducing
the Viscosity of Treatment Fluids Used in Subterranean Operations,"
filed on the same day, the entirety of which is herein incorporated
by reference.
BACKGROUND
[0002] The present invention relates to methods and compositions
for use in subterranean operations. More particularly, the present
invention relates to methods of reducing the viscosity of
subterranean treatment fluids that comprise a gelling agent
utilizing breakers that comprise hydroquinone and/or a derivative
thereof.
[0003] Treatment fluids may be used in a variety of subterranean
treatments, including, but not limited to, stimulation treatments
and sand control treatments. As used herein, the term "treatment,"
or "treating," refers to any subterranean operation that uses a
fluid in conjunction with a desired function and/or for a desired
purpose. The term "treatment," or "treating," does not imply any
particular action by the fluid or any particular component
thereof.
[0004] One common production stimulation operation that employs a
treatment fluid is hydraulic fracturing. Hydraulic fracturing
operations generally involve pumping a treatment fluid (e.g., a
fracturing fluid) into a well bore that penetrates a subterranean
formation at a sufficient hydraulic pressure to create or enhance
one or more cracks, or "fractures," in the subterranean formation.
The fracturing fluid may comprise particulates, often referred to
as "proppant," that are deposited in the fractures. The proppant
particulates, inter alia, prevent the fractures from fully closing
upon the release of hydraulic pressure, forming conductive channels
through which fluids may flow to the well bore. Once at least one
fracture is created and the proppant particulates are substantially
in place, the fracturing fluid may be "broken" (i.e., the viscosity
is reduced), and the fracturing fluid may be recovered from the
formation.
[0005] Treatment fluids are also utilized in sand control
treatments, such as gravel packing. In gravel-packing treatments, a
treatment fluid suspends particulates (commonly referred to as
"gravel particulates") for delivery to a desired area in a well
bore, e.g., near unconsolidated or weakly-consolidated formation
zones, to form a gravel pack to enhance sand control. One common
type of gravel-packing operation involves placing a sand control
screen in the well bore and packing the annulus between the screen
and the well bore with the gravel particulates of a specific size
to prevent the passage of formation sand. The gravel particulates
act, inter alia, to prevent the formation particulates from
occluding the screen or migrating with the produced hydrocarbons,
and the screen acts, inter alia, to prevent the particulates from
entering the production tubing. Once the gravel pack is
substantially in place, the viscosity of the treatment fluid may be
reduced to allow it to be recovered. In some situations, fracturing
and gravel-packing treatments are combined into a single treatment
(commonly referred to as "frac pack" operations). In such "frac
pack" operations, the treatments are generally completed with a
gravel pack screen assembly in place with the hydraulic fracturing
treatment being pumped through the annular space between the casing
and screen. In this situation, the hydraulic fracturing treatment
ends in a screen-out condition, creating an annular gravel pack
between the screen and casing. In other cases, the fracturing
treatment may be performed prior to installing the screen and
placing a gravel pack.
[0006] Maintaining sufficient viscosity in these treatment fluids
is important for a number of reasons. Maintaining sufficient
viscosity is important in fracturing and sand control treatments
for particulate transport and/or to create or enhance fracture
width. Also, maintaining sufficient viscosity may be important to
control and/or reduce fluid-loss into the formation. Moreover, a
treatment fluid of a sufficient viscosity may be used to divert the
flow of fluids present within a subterranean formation (e.g.,
formation fluids, other treatment fluids) to other portions of the
formation, for example, by "plugging" an open space within the
formation. At the same time, while maintaining sufficient viscosity
of the treatment fluid often is desirable, it also may be desirable
to maintain the viscosity of the treatment fluid in such a way that
the viscosity may be reduced at a particular time, inter alia, for
subsequent recovery of the fluid from the formation.
[0007] To provide the desired viscosity, polymeric gelling agents
may be added to the treatment fluids. Examples of commonly used
polymeric gelling agents include, but are not limited to, guar gums
and derivatives thereof, cellulose derivatives, biopolymers,
polysaccharides, synthetic polymers, and the like. To further
increase the viscosity of a treatment fluid, often the molecules of
the gelling agent are "crosslinked" with the use of a crosslinking
agent. Conventional crosslinking agents usually comprise a metal
ion that interacts with at least two polymer molecules to form a
"crosslink" between them.
[0008] At some point in time, e.g., after a viscosified treatment
fluid has performed its desired fuction, the viscosity of the
viscosified treatment fluid should be reduced. This is often
referred to as "breaking the gel" or "breaking the fluid." This can
occur by, inter alia, reversing the crosslink between crosslinked
polymer molecules, breaking down the molecules of the polymeric
gelling agent, or breaking the crosslinks between polymer
molecules. The use of the term "break" herein incorporates at least
all of these mechanisms. Certain breakers that are capable of
breaking treatment fluids comprising crosslinked gelling agents are
known in art. For example, breakers comprising sodium bromate,
sodium chlorite, and other oxidizing agents have been used to
reduce the viscosity of treatment fluids comprising crosslinked
polymers. Examples of such breakers are described in U.S. Pat. No.
5,759,964 to Shuchart, et al., and U.S. Pat. No. 5,413,178 to
Walker, et al., the relevant disclosures of which are herein
incorporated by reference. However, many of these breakers are only
effective in reducing the viscosity of a treatment fluid at
neutral-to-alkaline pH levels (i.e., above about pH 6). Excessive
concentrations of those breakers and/or additional catalysts may be
required to effectively reduce the viscosity of a treatment fluid
at lower pH levels (e.g., below about pH 6). High concentrations of
breaker and/or additional catalysts may be problematic since they
may, among other things, increase the cost and complexity of a
treatment fluid, adversely affect other components of the treatment
fluid, and/or leave damaging residues in the subterranean
formations where they are used.
SUMMARY
[0009] The present invention relates to methods and compositions
for use in subterranean operations. More particularly, the present
invention relates to methods of reducing the viscosity of
subterranean treatment fluids that comprise a gelling agent
utilizing breakers that comprise hydroquinone and/or a derivative
thereof.
[0010] In one embodiment, the present invention provides a method
comprising: providing a treatment fluid that comprises an aqueous
base fluid and a gelling agent; providing a breaker that comprises
a hydroquinone component; allowing the breaker to interact with the
treatment fluid; and allowing the viscosity of the treatment fluid
to reduce.
[0011] In another embodiment, the present invention provides a
method comprising: providing a treatment fluid that comprises an
aqueous base fluid, a gelling agent, and a breaker that comprises a
hydroquinone component; introducing the treatment fluid into the
portion of the subterranean formation; and allowing the viscosity
of the treatment fluid to reduce.
[0012] In another embodiment, the present invention provides a
method comprising: providing a treatment fluid that comprises an
aqueous base fluid and a gelling agent; providing a breaker that
comprises a hydroquinone component; introducing the treatment fluid
into a portion of the subterranean formation at or above a pressure
sufficient to create or enhance one or more fractures in a portion
of the subterranean formation; allowing the breaker to interact
with the treatment fluid; and allowing the viscosity of the
treatment fluid to reduce.
[0013] The features and advantages of the present invention will be
apparent to those skilled in the art. While numerous changes may be
made by those skilled in the art, such changes are within the
spirit of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] These drawings illustrate certain aspects of some of the
embodiments of the present invention, and should not be used to
limit or define the invention.
[0015] FIG. 1 illustrates data regarding the change in viscosity
over time of various treatment fluids, including certain
embodiments of the treatment fluids of the present invention.
[0016] FIG. 2 illustrates other data regarding the change in
viscosity over time of various treatment fluids, including certain
embodiments of the treatment fluids of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] The present invention relates to methods and compositions
for use in subterranean operations. More particularly, the present
invention relates to methods of reducing the viscosity of
subterranean treatment fluids that comprise a gelling agent
utilizing breakers that comprise hydroquinone and/or a derivative
thereof.
[0018] The treatment fluids of the present invention generally
comprise an aqueous base fluid, a gelling agent, and a breaker of
the present invention that comprises a hydroquinone component. In
certain embodiments, the gelling agent may comprise a "crosslinked
gelling agent," which is defined herein to mean that at least a
portion of the gelling agent may be crosslinked by a crosslinking
reaction comprising a crosslinking agent. The term "hydroquinone
component" is used herein to refer to hydroquinone or a derivative
thereof. The term "derivative" is defined herein to include any
compound that is made from the base compound, for example, by
replacing one atom in the base compound with another atom or group
of atoms. It is believed that breakers of the present invention may
reduce the viscosity of a treatment fluid comprising a gelling
agent and/or a crosslinked gelling agent at a pH in the range from
about 3 to about 12 with lower concentrations of breaker than the
concentration of a conventional breaker that would be required to
achieve the same results. In certain embodiments, a breaker of the
present invention may be used according to the present invention to
reduce the viscosity of a treatment fluid comprising a gelling
agent and/or a crosslinked gelling agent, wherein the pH of the
treatment fluid is in the range from about 4 to about 6.
[0019] The aqueous base fluid used in the treatment fluids of the
present invention may comprise fresh water, saltwater (e.g., water
containing one or more salts dissolved therein), brine, seawater,
or combinations thereof. Generally, the water may be from any
source, provided that it does not contain components that might
adversely affect the stability and/or performance of the treatment
fluids of the present invention, for example, copper ions, iron
ions, or certain types of organic materials (e.g., lignin). In
certain embodiments, the density of the aqueous base fluid can be
increased, among other purposes, to provide additional particle
transport and suspension in the treatment fluids of the present
invention. In certain embodiments, the pH of the aqueous base fluid
may be adjusted (e.g., by a buffer or other pH adjusting agent),
among other purposes, to activate a crosslinking agent, and/or to
reduce the viscosity of the treatment fluid (e.g., activate a
breaker, deactivate a crosslinking agent). In these embodiments,
the pH may be adjusted to a specific level, which may depend on,
among other factors, the types of gelling agents, crosslinking
agents, and/or breakers included in the treatment fluid. One of
ordinary skill in the art, with the benefit of this disclosure,
will recognize when such density and/or pH adjustments are
appropriate.
[0020] The gelling agents utilized in the present invention may
comprise any polymeric material capable of increasing the viscosity
of an aqueous fluid. In certain embodiments, the gelling agent may
comprise polymers that have at least two molecules that are capable
of forming a crosslink in a crosslinking reaction in the presence
of a crosslinking agent, and/or polymers that have at least two
molecules that are so crosslinked (i.e., a crosslinked gelling
agent). The gelling agents may be naturally-occurring, synthetic,
or a combination thereof. In certain embodiments, suitable gelling
agents may comprise polysaccharides, and derivatives thereof that
contain one or more of these monosaccharide units: galactose,
mannose, glucoside, glucose, xylose, arabinose, fructose,
glucuronic acid, or pyranosyl sulfate. Examples of suitable
polysaccharides include, but are not limited to, guar gums (e.g.,
hydroxyethyl guar, hydroxypropyl guar, carboxymethyl guar,
carboxymethylhydroxyethyl guar, and carboxymethylhydroxypropyl guar
("CMHPG")), cellulose derivatives (e.g., hydroxyethyl cellulose,
carboxyethylcellulose, carboxymethylcellulose, and
carboxymethylhydroxyethylcellulose), and combinations thereof. In
certain embodiments, the gelling agents comprise an organic
carboxylated polymer, such as CMHPG. In certain embodiments, the
derivatized cellulose is a cellulose grafted with an allyl or a
vinyl monomer, such as those disclosed in U.S. Pat. Nos. 4,982,793;
5,067,565; and 5,122,549, the relevant disclosures of which are
incorporated herein by reference. Additionally, polymers and
copolymers that comprise one or more functional groups (e.g.,
hydroxyl, cis-hydroxyl, carboxylic acids, derivatives of carboxylic
acids, sulfate, sulfonate, phosphate, phosphonate, amino, or amide
groups) may be used.
[0021] The gelling agent may be present in the treatment fluids of
the present invention in an amount sufficient to provide the
desired viscosity. In some embodiments, the gelling agents may be
present in an amount in the range of from about 0.12% to about 2.0%
by weight of the treatment fluid. In certain embodiments, the
gelling agents may be present in an amount in the range of from
about 0.18% to about 0.72% by weight of the treatment fluid.
[0022] In those embodiments of the present invention wherein it is
desirable to crosslink the gelling agent, the treatment fluid may
comprise one or more of the crosslinking agents. The crosslinking
agents may comprise a metal ion that is capable of crosslinking at
least two molecules of the gelling agent. Examples of suitable
crosslinking agents include, but are not limited to, borate ions,
zirconium IV ions, titanium IV ions, aluminum ions, antimony ions,
chromium ions, iron ions, copper ions, and zinc ions. These ions
may be provided by providing any compound that is capable of
producing one or more of these ions; examples of such compounds
include, but are not limited to, boric acid, disodium octaborate
tetrahydrate, sodium diborate, pentaborates, ulexite, colemanite,
zirconium lactate, zirconium triethanol amine, zirconium lactate
triethanolamine, zirconium carbonate, zirconium acetylacetonate,
zirconium malate, zirconium citrate, zirconium diisopropylamine
lactate, zirconium glycolate, zirconium triethanol amine glycolate,
zirconium lactate glycolate, titanium lactate, titanium malate,
titanium citrate, titanium ammonium lactate, titanium
triethanolamine, and titanium acetylacetonate, aluminum lactate,
aluminum citrate, antimony compounds, chromium compounds, iron
compounds, copper compounds, zinc compounds, and combinations
thereof. In certain embodiments of the present invention, the
crosslinking agent may be formulated to remain inactive until it is
"activated" by, among other things, certain conditions in the fluid
(e.g., pH, temperature, etc.) and/or contact with some other
substance. In some embodiments, the crosslinking agent may be
delayed by encapsulation with a coating (e.g., a porous coating
through which the breaker may diffuse slowly, or a degradable
coating that degrades downhole) that delays the release of the
crosslinking agent until a desired time or place. The choice of a
particular crosslinking agent will be governed by several
considerations that will be recognized by one skilled in the art,
including but not limited to the following: the type of gelling
agent included, the molecular weight of the gelling agent(s), the
pH of the treatment fluid, temperature, and/or the desired time for
the crosslinking agent to crosslink the gelling agent
molecules.
[0023] When included, suitable crosslinking agents may be present
in the treatment fluids of the present invention in an amount
sufficient to provide, inter alia, the desired degree of
crosslinking between molecules of the gelling agent. In certain
embodiments, the crosslinking agent may be present in the treatment
fluids of the present invention in an amount in the range of from
about 0.0005% to about 0.2% by weight of the treatment fluid. In
certain embodiments, the crosslinking agent may be present in the
treatment fluids of the present invention in an amount in the range
of from about 0.001% to about 0.05% by weight of the treatment
fluid. One of ordinary skill in the art, with the benefit of this
disclosure, will recognize the appropriate amount of crosslinking
agent to include in a treatment fluid of the present invention
based on, among other things, the temperature conditions of a
particular application, the type of gelling agents used, the
molecular weight of the gelling agents, the desired degree of
viscosification, and/or the pH of the treatment fluid.
[0024] The breakers of the present invention comprise a
hydroquinone component. The term "hydroquinone component" is used
herein to refer to hydroquinone or a derivative thereof.
Derivatives of hydroquinone that may be used in the present
invention include, but are not limited to, semiquinone,
benzoquinone, catechol, quinhydrone charge-transfer complexes, and
the like. In certain embodiments of the present invention, the
breaker may comprise a combination of a hydroquinone component and
an "additional breaker component," which herein refers to any other
breaker known in the art. Examples of suitable additional breakers
include, but not limited to, sodium chlorite, sodium bromate,
sodium persulfate, sodium peroxydisulfate, ammonium chlorite,
ammonium bromate, ammonium persulfate, ammonium peroxydisulfate,
potassium chlorite, potassium bromate, potassium persulfate,
postassium peroxydisulfate, one or more oxidizable metal ions
(i.e., a metal ion whose oxidation state can be increased by the
removal of an electron, such as copper, cobalt, iron, manganese,
vanadium), and the like. Examples of such additional breakers are
described in U.S. Pat. No. 5,759,964 to Shuchart, et al., and U.S.
Pat. No. 5,413,178 to Walker, et al., the relevant disclosures of
which are herein incorporated by reference. In certain embodiments
of the present invention, the breaker may be formulated to remain
inactive until it is "activated" by, among other things, certain
conditions in the fluid (e.g., pH, temperature, etc.) and/or
contact with some other substance. In some embodiments, the breaker
may be delayed by encapsulation with a coating (e.g., a porous
coating through which the breaker may diffuse slowly, or a
degradable coating that degrades down hole) that delays the release
of the breaker until a desired time or place.
[0025] The breaker should be present in the treatment fluids of the
present invention in an amount sufficient to provide the desired
viscosity reduction. In certain embodiments, the breaker may be may
be present in the treatment fluids of the present invention such
that the concentration of the hydroquinone component is in the
range of from about 0.001% to about 0.3% by weight of the treatment
fluid. In certain embodiments, the breaker may be may be present in
the treatment fluids of the present invention such that the
concentration of the hydroquinone component is in the range of from
about 0.001% to about 0.025% by weight of the treatment fluid. The
amount and composition of the breaker utilized in the present
invention may depend upon a number of factors, including
temperature, the type and/or amount of gelling agents used, the
type and/or amount of crosslinking agent used, the pH of the
treatment fluid, and the like. One skilled in the art, with the
benefit of this disclosure, will recognize the amount and type of
breaker suitable for a particular application of the present
invention.
[0026] The treatment fluids of the present invention optionally may
comprise one or more additional additives known in the art,
including, but not limited to, fluid loss control additives, gel
stabilizers, gas, salts (e.g., KC1), pH-adjusting agents (e.g.,
buffers), corrosion inhibitors, dispersants, flocculants, acids,
foaming agents, antifoaming agents, H.sub.2S scavengers,
lubricants, oxygen scavengers, weighting agents, scale inhibitors,
surfactants, catalysts, clay control agents, biocides, friction
reducers, particulates (e.g., proppant particulates, gravel
particulates), combinations thereof, and the like. For example, a
gel stabilizer compromising sodium thiosulfate may be included in
certain treatment fluids of the present invention. Individuals
skilled in the art, with the benefit of this disclosure, will
recognize the types of additives that may be suitable for a
particular application of the present invention. For example,
particulates may be included in the treatment fluids of the present
invention in certain types of subterranean operations, including
fracturing operations, gravel-packing operations, and the like.
[0027] The methods of the present invention generally comprise:
providing a treatment fluid of the present invention comprising an
aqueous base fluid and a gelling agent; providing a breaker
comprising a hydroquinone component; allowing the breaker to
interact with the treatment fluid; and allowing the breaker to at
least partially reduce the viscosity of the treatment fluid. In
certain embodiments, the gelling agent may comprise a crosslinked
gelling agent. The breaker comprising the hydroquinone component
may be provided separately or as a component of the treatment fluid
in practicing the methods of the present invention. For example,
the breaker comprising the hydroquinone component may be added to
the treatment fluid as it is pumped into a portion of a
subterranean formation through a well bore penetrating the
subterranean formation. In some embodiments, the methods of the
present invention further comprise introducing the treatment fluid
into at least a portion of a subterranean formation. In those
embodiments, at least a portion of the gelling agent may be or
become a crosslinked gelling agent prior to, during, or subsequent
to introducing the treatment fluid into the subterranean formation.
For example, the crosslinking agent may be formulated to crosslink
the gelling agent at some time after the treatment fluid is
introduced into the subterranean formation.
[0028] The treatment fluid may be provided and introduced into the
subterranean formation in certain embodiments of the present
invention by any means known in the art. The treatment fluid may be
prepared at the job site, or certain components of the treatment
fluid (e.g., the aqueous base fluid and the gelling agent) may be
pre-mixed several hours prior to use and then transported to the
job site. Certain components of the treatment fluid may be provided
as a "dry mix" to be combined with the aqueous base fluid and/or
other components prior to or during introducing the treatment fluid
into the subterranean formation. In certain embodiments, the
treatment fluid may be introduced into the subterranean formation
by pumping the treatment fluid into a well bore that penetrates a
portion of the subterranean formation. In certain embodiments
(e.g., fracturing operations), the treatment fluid may be
introduced into the subterranean formation at or above a pressure
sufficient to create or enhance one or more fractures in a portion
of the subterranean formation. In certain embodiments, the
treatment fluid may comprise a plurality of particulates (e.g.,
sand, gravel, bauxite, ceramic materials, glass materials, polymer
materials, wood, fibrous materials, and/or composite particulates),
which may be used, inter alia, to prop open one or more fractures
in the subterranean formation and/or to form a gravel pack in or
adjacent to a portion of the subterranean formation.
[0029] The breaker may be allowed to at least partially reduce the
viscosity of the treatment fluid at any point in the course of the
treatment, for example, at the conclusion of a particular treatment
of a subterranean formation in order to facilitate recovery of the
fluid from the formation. In certain embodiments, the viscosity of
the treatment fluid may be reduced and the treatment fluid may be
recovered so as to deposit particulates therein in at least a
portion of the subterranean formation and/or one or more fractures
therein.
[0030] The methods of the present invention may be used in any
subterranean operation involving the introduction of a treatment
fluid into a subterranean formation wherein the viscosity of the
treatment fluid is reduced, including, but not limited to,
fracturing operations, gravel-packing operations, frac-packing
operations, well bore cleanout operations, and the like. In certain
embodiments of the present invention, the treatment fluid may be
introduced into a portion of a subterranean formation so as to
create a "plug" capable of diverting the flow of fluids present
within the subterranean formation (e.g., formation fluids, other
treatment fluids) to other portions of the formation. In those
embodiments, the breaker then may be allowed to reduce the
viscosity of the fluid forming the "plug," which may at least
partially restore the flow of fluids through that portion of the
subterranean formation.
[0031] To facilitate a better understanding of the present
invention, the following examples of certain aspects of some
embodiments are given. In no way should the following examples be
read to limit, or define, the scope of the invention.
EXAMPLE 1
[0032] Three samples of treatment fluids were mixed in a Waring
Blender, the samples comprising 0.42% by weight CMHPG gelling
agent, 0.0016% by weight zirconium glycolate crosslinking agent,
and 2% by weight KC1, in tap water obtained in Duncan, Okla. The pH
of each fluid sample was adjusted to 4.9.+-.0.1 with about 0.1% to
about 0.15% by weight ammonium acetate-acetic acid buffer.
Additionally, the following components were added to the three
fluid samples: no additional additives to Fluid Sample A; 0.12% by
weight sodium bromate breaker added to Fluid Sample B; and 0.003%
by weight hydroquinone added to Fluid Sample C (a sample of a
treatment fluid of the present invention).
[0033] Viscosity measurements of each fluid were taken on a
Fann.RTM. 50 viscometer equipped with a 420 spring, a 316SS cup and
B2X bob according to the following procedure. The bath was
preheated to 200.degree. F. A 60 mL sample of each fluid was
transferred to the viscometer cup at 75.degree. F. and placed on
the viscometer. The cup was rotated at 106 rpm (40 sec.sup.-1)
until the first scan was begun. Shear rate scans were measured for
2 min each at 150, 106, 75, 53, 37, 26 and 18 sec.sup.-1, with 3
min at 40 sec.sup.-1 in between scans. Viscosity measurements were
taken over a period of almost 140 minutes. A plot of time (min)
versus viscosity (cP) for each sample is provided in FIG. 1.
[0034] Thus, Example 1 illustrates that breakers comprising
hydroquinone may reduce the viscosity of a treatment fluid more
effectively than conventional breakers.
EXAMPLE 2
[0035] Five samples of treatment fluids were mixed in a Waring
Blender, the samples comprising 0.42% by weight CMHPG gelling
agent, 0.0016% by weight zirconium glycolate crosslinking agent, 2%
by weight KC1, and 0.06% by weight sodium thiosulfate gel
stabilizer, in tap water obtained in Duncan, Okla. The pH of each
fluid sample was adjusted to 4.9.+-.0.1 with about 0.1% to about
0.15% by weight acetate-acetic acid buffer. Additionally, the
following components were added to each of the five fluid samples:
no additional additives to Fluid Sample D; 0.12% by weight sodium
bromate breaker added to Fluid Sample E; 0.12% by weight sodium
bromate breaker and 0.003% by weight hydroquinone added to Fluid
Sample F (a sample of a treatment fluid of the present invention);
0.3% by weight sodium bromate breaker added to Fluid Sample G; and
0.3% by weight sodium bromate breaker and 0.012% by weight
hydroquinone added to Fluid Sample H (a sample of a treatment fluid
of the present invention).
[0036] Viscosity measurements of each fluid were taken according to
the procedure described in Example 1. A plot of time (min) versus
viscosity (cP) for each sample is provided in FIG. 2.
[0037] Thus, Example 2 illustrates that breakers comprising
hydroquinone, in combination with other types of breakers, may
reduce the viscosity of a treatment fluid more effectively than
conventional breakers alone.
[0038] Therefore, the present invention is well adapted to attain
the ends and advantages mentioned as well as those that are
inherent therein. While numerous changes may be made by those
skilled in the art, such changes are encompassed within the spirit
of this invention as defined by the appended claims. The terms in
the claims have their plain, ordinary meaning unless otherwise
explicitly and clearly defined by the patentee.
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